Advice needed - DIY off-grid solar electrics DC charging via AC from generator Answered
Hi all, new to this forum... I'm looking for some advice regarding an off-grid electrics setup i'm running. Currently i have a PV solar panel charging a battery bank through a charge controller. It's a 12vdc system. For 240vac i use a small (500W) inverter. For larger loads i use a diesel generator. The inverter is basic but very high quality sine wave, it doesn't do any charging nor does it automatically switch the load between the AC of the generator and its own AC (i do this manually). In order to recharge my batteries when there isnt enough sun (which is often!), i use a simple AC powered charger that isnt specifically designed for off-grid/solar applications. In other words it is not "intelligent" and doesnt have bulk, float or equalization settings - it's just a DC charger that gives decreasing current as the voltage of the batteries rises. In fact it is very prone to overcharging if left charging for too long and will keep putting current into the batteries even after they've reached 15.5vdc or more.
My question is this: is it a good idea to feed the DC charging current from my AC-fed charger into my solar charge controller in order to allow the charge controller to regulate and/or limit the charge as appropriate? I did this for a period of time and it seemed not to cause any problems. However, my AC charger did eventually blow its recrifying diodes although i'm not sure if this was due to a separate issue with the AC power coming from my generator which at the time was an old one and may not have been giving proper AC voltage (it may have been low due to engine speed problems).
The solar charge controller is a PWM type. The way i had it set up was the DC from the solar panel and the DC from the charger in parallel to the charge controller.
If there is no difference between the DC from the charger and the DC from the solar panel, i don't see how there could be any problem as it amounts to the same thing as having two 12v PV panels in parellel. However, what i dont know (due to insufficient technical knowledge) is whether rectified DC is any different to the DC from a solar panel.
My setup is as follows:
1 x 200W 12vdc PV panel
60A tristar PWM solar charge controller
2 x 6vdc Trojan t105 batteries wired in series to give 12vdc
Mastervolt 500w pure sine wave inverter (12vdc in, 240vAC out)
SDMO 6kva diesel generator (240vAC)
Wolf Max 50 battery charger (AC powered 40A DC charger)